Methods for producing regenerated cellulosic fibers by the use of an NMMO-containing solvent have been known for a long time, as disclosed in JP-B 57-11566 and JP-B 60-28848, for example. The conventional methods of production utilizing the above solvent, however, have a serious drawback that the resulting regenerated cellulosic fibers are liable to cause fibrillation, which has become a hindrance to their general application. In spite of such a drawback, these methods have recently attracted attention again because they are environmentally friendly and are useful from an economical point of view and the resulting regenerated fibers have good physical properties to a certain extent as compared with the rayon process.
As for the above problem of fibrillation, many studies for solving the problem have been made, and some patent applications have been filed, as seen from JP-A 8-501356, JP-A 7-508320, and JP-A 8-49167, for example. In actual cases, however, these studies have not yet reached to the level that satisfactory effects can be obtained on a practical scale.
In the case where the regenerated cellulosic fibers produced by the use of the above solvent are applied to the filed of clothing or the like, it is believed that the formation of a hollow or non-circular cross section is useful for improving the luster or feeling of these fibers themselves or when they are made into woven or knitted fabrics. Notwithstanding, no studies have been made so far on the regenerated cellulosic fibers with a hollow or non-circular cross section produced by the use of an NMMO-containing solvent.
Furthermore, no one has considered using cellulose materials for the purpose of making a contribution to the preservation of global environment nor utilizing cellulose materials containing hemicellulose and lignin in large quantities.
The present invention has been made under the above circumstances with the objects of overcoming the problem of fibrillation which is found as a drawback of regenerated cellulosic fibers produced by the use of an NMMO-containing solvent as described above, as well as, in particular, of providing regenerated cellulosic fibers having excellent physical properties, feeling, dyeability and other properties for use in clothing, and of establishing a process of manufacture ensuring their stable production.